Cyclical redundancy checking circuits are well known. However they typically use a serial logic configuration comprising a 16-bit shift register with four outputs fed back to exclusive-or logic at the input. An example of such a circuit is the Hewlett Packard Signature Analysis System.
This serial configuration of the prior art requires that each data bit be clocked serially into the cyclical redundancy checking circuit. The time required to perform this operation is therefore equivalent to the number of bits per sample multiplied by the period of the CLOCK signal. For many applications such an arrangement requires more time than is allowed between successive input data groups.
Accordingly the present invention provides a high speed cyclic redundancy checking circuit capable of determining the validity of multiple, high frequency, cyclical parallel groups of data on a time-sharing basis.